Owing to the high density of the vapor of the chlorinated solvents normally used in solvent vapor degreasers, there is normally relatively little loss quantitatively. Unfortunately, such loss as does occur is a subject of concern: chlorinated solvents are implicated in liver damage, various cancers, smog formation, and upper-atmosphere photochemical reactions tending to remove the ozone layer. If solvent losses could be reduced by an order of magnitude, or if nonchlorinated solvents could be used without creating a fire hazard, a substantial improvement in safety would be achieved. In either case, it is important that the solvent vapors be kept in the degreasing tank and not be permitted to escape to the atmosphere.